Arthropodic digestion: could insects help tackle food waste?

The Environment Bill, currently making its way through the UK Parliament, contains a provision to improve recycling rates by mandating weekly separate collections of household and commercial food waste. Currently, only 51% of local authorities in England collect food waste separately from residual waste. Of those, a quarter collect it mixed with garden waste, which is not straightforwardly consistent with what the Bill proposes.

If all local authorities implemented a weekly household food waste collection, Defra estimates that England would collect an additional 1.35 million tonnes of food waste a year by 2029. However, the Bill is silent regarding what will happen to all this food waste.

A lot to digest

So-called ‘wet’ anaerobic digestion (AD) is currently the dominant technology for treating food waste, and the default assumption would be that far more AD capacity will be needed in future. However, there may be limits on the extent to which it is feasible to increase its use.

In addition to producing biogas, AD also generates a nitrate-rich digestate as an output. This can be spread to land as a bio-fertiliser, which can reduce the need for artificial fertiliser. However, about 55% of land in England falls within Nitrate Vulnerable Zones (NVZs), where special rules are in place to limit the risk of nitrate pollution of watercourses. NVZs have strict limits on the times of year when digestate and other high readily available nitrogen manures can be applied to land, and how much nitrogen can be applied to it.

In some localities in England, spreading large amounts of additional digestate will not be permissible. It isn’t economically viable to transport digestate long distances, and this may constrain the extent to which AD – especially wet AD – can be used to treat food waste. If so, other options will have to be explored. These might include co-locating AD facilities with existing facilities dealing with garden waste, and blending the output from AD with the material being composted aerobically, or using higher solids AD processes. Alternatively, they might involve rather different approaches to managing food waste.

Big fish eat little fish

Meanwhile, the Government’s aim to manage the marine environment more sustainably has brought how we operate fisheries under greater scrutiny. The majority of fish farmed in the UK are fed a diet made up of wild-caught fish and fish oil, as well as soya bean, protein concentrates and vegetable oils. The production of fishmeal and fish oil has been linked to highly unsustainable fishing practices globally, which implicate European aquafeed companies. Producing even the vegetable based components of fishmeal is uses land and other resources, and is not without cost. Finding a new, more sustainable source of feed would be a big step towards improving circularity in the aquaculture sector, though the sector also faces other challenges.

Perhaps surprisingly, there may be a way to tackle both our food waste problem and unsustainable fisheries simultaneously. A 2017 relaxation in EU legislation on the use of animal by-products to feed animals has allowed some species of insect to be bred as feed for aquaculture. As animal feed, insects have a high protein content and are highly digestible, and they can be reared rapidly and efficiently at a small scale.

However, while insects can be reared on a range of waste products, including household food waste, EU and UK law on animal by-products restricts how food waste from commercial and household kitchens is managed. Guidance makes clear that such waste can only be disposed of via a limited range of routes, including incineration and anaerobic digestion. Only a limited range of food wastes, such as baked goods, vegetables, pasta, chocolate, sweets, and breakfast cereals, from sources such as manufacturers and retailers, can be fed to animals, including insects (although the regulations weren’t written with insects in mind).

UK-based insect farms companies, such as London-based Entocycle, therefore rear black soldier fly larvae on source-separated food waste from pre-consumer sources, like rejected supermarket fruit and vegetables, brewer’s grains and coffee grounds. The larvae are then pelletised for use as feed for fish farms in Scotland. Entocycle predicts there will be sufficient production volume to replace 30% of fishmeal in the entire Scottish Salmon industry by 2025. But if more food wastes could be used to produce insect protein, the sector has considerable potential for growth.

Fly in the ointment

As things stand, the prohibition on using household food waste and other catering waste as a feeding substrate remains. It is to be lifted unless it can be demonstrated that it is safe to do so.

Some efforts have been made to study the issue. The European Food Safety Authority produced a risk profile on the safety of insects as food and feed. The study examined a variety of possible risks, including the transfer of viruses, bacteria, parasites, fungi and prions – the last of which risks was a major consideration in the updating of animal by-product regulations in the wake of the BSE crisis in the 1990s. The study found that, while evidence was thin,

“In general, food and feed-grade substrates, if maintained in good hygienic conditions, should not pose any additional risk when fed to insects as compared with other approved foods or feeds.”

However, it concluded that, although insects don’t produce or amplify prions, some studies suggested that:

“Insects farmed on a substrate or in an environment in which infectious prions are present could act as mechanical vectors of infection”.

So, if insects are fed on waste that contains infectious prions, these prions may remain within them at the point when the insects are harvested. Due to the limitations on the evidence, though, the study called for specific evaluation of the risks around feeding insects on materials such as catering waste.

Flying the flag

In order to open up the possibility of new, innovative techniques to process food waste, the insect protein sector is likely to need to develop evidence that the use of household food waste as insect feed is safe. The EU is looking at further relaxations on the use of insect protein, with discussions taking place regarding the possibility of allowing it to be used as poultry and pig feed – the main issue seeming to be a lack of political support. However, there is little indication of progress on exploring whether the range of food waste that can be fed to insects could be safely expanded.

There is perhaps an opportunity for the UK, outside the EU, to take the lead in researching this area. That research would ideally be made a priority so as to allow this approach to be adopted as part of the solution to the source separated food waste that will result from new legislation. Indeed, given emerging evidence regarding the safety of other means of feeding food waste to livestock, it would be a timely moment for the UK to reconsider the evidence regarding the safety of other ways of using food waste which are currently forbidden.

In the meantime, though, there is nothing to stop us from planning for insect protein production to take in more industrial food waste, thereby freeing up capacity in existing AD plants.

Insect protein could prove to be a sustainable alternative to wild caught fish and other land intensive crops used for aquaculture feed, helping to grow the bioeconomy in the UK and elsewhere. It offers a win-win solution for responsibly managing supply chains for aquaculture, while dealing with the UK’s food waste surplus problem at the same time. This potential should be seriously and urgently explored.

Featured image: WRAP